CVE-2023-39953

What it is

user_oidc provides the OIDC connect user backend for Nextcloud, an open-source cloud platform. Starting in version 1.0.0 and prior to version 1.3.3, missing verification of the issuer would have allowed an attacker to perform a man-in-the-middle attack returning corrupted or known token they also have access to. user_oidc 1.3.3 contains a patch. No known workarounds are available.

At a glance

Exploitability

Can be exploited over the network without logging in. Limited direct impact.

Exploit odds

0.5% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2023-08-10 14:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 06:13 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.5% in the next 30 days (EPSS).
• Severity: 4.8 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2023-08-10 14:15 UTC

Last modified

2026-06-17 06:13 UTC

Exploit probability

0.5% · EPSS, next 30 days

Weakness

CWE-303

Record status

Modified

Affected

• Nextcloud User Oidc < 1.3.3

Attack profile CVSS 3.1 · 4.8

Attack vector

Network

Complexity

High

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

Low

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2023-39953.md and follow it. Check whether this project is affected by CVE-2023-39953. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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